This invention relates to packaging and more particularly to a novel and improved web of side connected open bags and a process of packaging with such a web.
U.S. Pat. No. 5,743,070, issued Apr. 28, 1995 to Hershey Lerner and Dana J. Liebhart under the title of PACKAGING MACHINE, MATERIAL AND METHOD, discloses a machine and process of packaging with side connected bags. U.S. Pat. No. 5,944,424 of Aug. 31, 1999 is a patent issuing from a divisional application which claims the packaging web as disclosed in both patents (the SP Patents).
With the machine of the SP Patents, webs of side connected bags are used. Each web is an elongated, flattened, plastic tube which includes a top section which itself is essentially a tube. In use the top section is fed over a mandrel and past a slitter which separates the top section into two upstanding lips. The lips are grasped by unique belts that are fed along divergent paths of travel into parallel paths through a load station. The unique belts are described more fully in U.S. Pat. No. 5,722,218 issued Mar. 3, 1998 to Hershey Lerner under the title PLASTIC TRANSPORT SYSTEM (herein xe2x80x9cthe Belt Patentxe2x80x9d). The disclosures of the SP Patents and the Belt Patent are incorporated by reference.
Each web includes side connected bags which depend from the lips. As a web is fed along its path of travel through a machine of the SP Patent (the SP Machine), lines of weakness interconnecting sides of adjacent bags are ruptured to leave individual bags depending from the lips.
As the belts diverge, the gripped lips are separated from the depending bags along lines of weakness to the extent necessary to cause the bags to span the space between the parallel paths in a generally rectangular opening.
As indicated in U.S. Pat. No. 6,035,611 issued Mar. 14, 2000 and disclosing an improved process of making such a web, (the Process Patent) the system disclosed in the SP patents has, on occasion, experienced difficulty. More specifically, there is a tendency for bags to fail to open in the intended rectangular shape because the separation of supporting lips from the front and back faces of the bags is not equal. This appears to be due, at least in part, to the manner in which a pair of lines of continuous perforations are formed along the web. Too often the webs are not perforated evenly in both the front and back webs. This occurs because, toothed rotary knives used to form the continuous perforations, have pointed teeth. The teeth penetrate through one web into the other in forming the perforations. Since the teeth are pointed, the length of each perforation in the first penetrated web is greater than in the other.
While the process disclosed and claimed in the Process Patent has diminished the scope of the problem, there remains a problem in that all too often a lead portion of the bag will open to a greater extent than a trailing portion as the web is fed into and through a load station.
A somewhat similar system utilizes special guide tracks which support a specialized web. In one embodiment, that specialized web has upstanding lips, each of which has a section of an associated, continuous, enlarged top portion. The top portions are supports that are fed into the special guides that are in the form of tubes. The tubes are open at the bottom so that the web hangs from the enlarged portions. The web has a series of side connected bags suspended from the continuous top portions. Lead and trailing sections of each bag are slit an appropriate amount to permit the bag to open a desired amount and hopefully to a rectangular shape. Since neither the specialized guides nor the web can be adjusted, there is a need for precision in the manufacture which, given manufacturing tolerances, is at best difficult to obtain. Moreover, as the bags are fed to a load station, they are only supported in central portions and not throughout their longitudinal lengths. Further, because of the special guide tracks, the cost of making the guide tracks and a packaging web is greater than the cost of making a web for the SP Machine. Moreover in use change over from one packaging run to another is far simpler with the SP machine.
Accordingly, it would be desirable to refine the applicant""s system to provide a web in which bags reliably and consistently open to rectangular shapes and in which bags are more positively supported than the prior webs of the somewhat similar system to enable packaging of heavier objects. In addition it would be desirable to maintain the ease and speed of change over available with the web of the SP Patents from one packaging operation to another for a different product.
The present invention is directed to a web of side connected bags which web is an improvement over the webs disclosed and claimed in the SP and Process Patents. The improved web provides the web feed advantages over other prior art that are provided by the webs of the SP and Process Patents. In addition, the web of the present invention assures rectangular opening of bags as they are transported through a load station and enhanced load support enabling the packaging of heavier items than can be supported by the webs of the SP and Process Patents.
The improved web, like the predecessors, is an elongated flatten tube having face and back sides delineating the faces and backs of a set of side by side bags. The tube includes an elongated top section which is adapted to be slit to provide front and back web supporting lips. Spaced sets of side seals extend transversely upwardly from the bottom of the web to delineate sides of adjacent bags.
Unlike the webs of the SP and Process Patents, the tops of the bags each have a spaced pair of, rather than continous, lines of weakness. The spaced pair of each bag extend from further lines of weakness delineating the sides of the bags. The spaced pair of lines of each bag are each of length which is one-half the width of a desired bag opening when a bag is rectangularly configurred as it passes through the load station. The solid web sections between the spaced lines of weakness assure equal opening along the leading and trailing sides of each bag as it passes through the load station. The solid sections also provide enhanced load support for a given material of like chemistry and thickness. Thus heavier products can be packaged and forces resulting from a product being loaded striking a bag are better absorbed.
The improved web of the present invention produces a number of outstanding and indeed unexpected advantages. These advantages occur in both the equipment used to make the web and the equipment used in packaging products. The costs of manufacture and of packaging are both reduced because both the manufacturing and the packaging equipment can be run at higher speeds. Further, the precision required of equipment used to make the bags is reduced, contributing to a reduction in the cost of packaging.
The reduction in the cost of manufacturing and the higher on manufacturing through put achieved occur because the manufacturing tolerances with respect to the side seals and the perforations are far less rigid. The cost of making manufacturing machines is reduced by the elimination of such things as edge guides. The looser tolerances are achieved because there is less loading on the side seals during packaging. Tolerances in the lines of weakness along the tops of the bag are loosened because the packaging process now relies on the solid central sections of the web to control the extent of separation of the top lips from the bags as a web enters the packaging station.
In packaging operations higher through puts are achievable because the webs are better able to withstand forces that are occurring during the packaging operation. In addition for many products where support conveyors have been required in the past, the need for those support conveyors is eliminated.
Accordingly the objects of the invention are to provide a novel and improved packaging web and a method of packaging.